A flame test is an analytical technique to identify the presence of metal ions in a sample by heating the sample with a flame and examining the color of the flame. It is also used to visually determine the identity of an unknown metal or metalloid ion based on the characteristic color the salt turns the flame of an alcohol lamp. The heat of the flame excites the metals ions, causing them to emit visible light. The characteristic emission spectra can be used to differentiate between some elements. Different metal electrons emit different wavelengths of light to return to their respective ground states, so the flame colors are varied. These flames can be ...view middle of the document...
Elements may often be identified by the color they expose to a flame.
MATERIALS AND METHODS
In determining the flame colors of different metals, first of all make sure that you have a clean flame test wire or nichrome wire. Then after it, the loop of the nichrome wire must be heated in flames hottest region until there was no visible of color. There should be no change in color of the flame if it's clean and if it is not clean, clean it by dipping into the concentrated HCL provided, then hold the loop in the Alcohol lamp. Repeat this cleaning until there is no more change in the color of the flame. Next objective is to do the flame tests. Dip the nichrome wire's loop into the reagent solution, then hold the nichrome wire's loop in the hottest part of the alcohol lamp flame. After doing it, observe and make a note of the color of the flame on your Flame Test Chart. Clean the nichrome wire, then test another known reagent solution. Keep going until you have recorded the color of all of the known reagent solutions. Check results and then observe carefully and compute smoothly to avoid any mistake.
RESULTS AND DISCUSSIONS
When a metal or metal salt is burned, the input of thermal energy raises the electrons in the metal atom to a higher energy state. These electrons cannot remain in this excited state for too long and will emit energy in the form of light to return to more stable, grounded state. It is the light we see when a metal atom is burned in a flame.
In this experiment, we need to do some computations for us to know the energy, frequency of light and wavelength. Below are the equations used in the experiment:
|Correlation between wavelength and color |
|Wavelength (nm) |Color |
|380 – 435 |violet |
|435 – 480 |blue |
|480 – 490 |green-blue |
|490 – 500 |blue-green |
|500 – 560 |green |
|560 – 580 |yellow-green |
|580 – 595 |yellow |
|595 – 650 |orange |
|610 – 750 |red |
|[pic] (nm) |v (Hz) |E (J) |
| |from: c=[pic] | |
|[pic] | |E= hv |
| |[pic]= [pic] | |
|m= 1 [pic]-9nm | |where: |
| |where: |E = Energy of light |
| |v = frequency of light |h = Planck’s constant |
| |c = speed of light |v = frequency of light |
| |[pic]= wavelength | ...